An optical type pressure sensor for detecting e.g., pressure of a fluid in an optical type is formerly known as the optical device of this kind. FIGS. 9A to 9D are explanatory views showing this optical type pressure sensor, where FIG. 9A is a plan view, and FIG. 9B is a front view, and FIG. 9C is a partial enlarged view and FIG. 9D is a cross-sectional view seen from arrow IXD-IXD of FIG. 9C.
This optical type pressure sensor 50 has an optical waveguide path 51. Optical fibers 52, 53 are connected to both ends of the optical waveguide path 51. A Bragg grating 55 is formed in an intermediate portion of an optical path of the optical waveguide path 51. This Bragg grating 55 has a periodic structure in which concave portions (grooves) and convex portions are alternately formed. The Bragg grating 55 has a function for reflecting or transmitting only light of a constant wavelength.
The optical waveguide path 51 is adhered to one substrate face of a silicon substrate 56 by an adhesive layer 59. A glass substrate 54 is adhered to the other substrate face of the silicon substrate 56. A pressure receiving chamber 57 for flowing a fluid as a detecting object thereinto is formed in a portion constructed by the silicon substrate 56 and the glass substrate 54 and corresponding to a rear face of the Bragg grating 55. A diaphragm 58 is formed in a portion corresponding to the rear face of the Bragg grating 55 in this pressure receiving chamber 57 by thinly setting the silicon substrate 56. When the optical type pressure sensor 50 is used, an unillustrated light emitting element is connected to the optical fiber 52, and a light receiving element is connected to the optical fiber 53.
When the pressure of the fluid flowed into the pressure receiving chamber 57 is changed, the diaphragm 58 is displaced in the vertical direction, and an irregular periodic property of the Bragg grating 55 is changed. Thus, one portion of light emitted from the light emitting element to the optical waveguide path 51 and totally reflected on the Bragg grating 55 is transmitted through the Bragg grating 55, and is received by the light receiving element. The pressure of the fluid is detected on the basis of intensity, etc. of the light received by this light receiving element.
The above sensor is disclosed in, for example, “Technical Digest of 16th International Conference on Optical Fiber Sensors (2003) (pp. 694-697)” and JP-A-2000-221085
However, the above former optical type pressure sensor has a structure in which the optical waveguide path 51 is adhered to the silicon substrate 56 by the adhesive layer 59. Therefore, the pressure applied to the diaphragm 58 is buffered by the adhesive c layer 59. Therefore, a problem exists in that it is inferior in detecting accuracy of the pressure.
Further, a problem also exists in that manufacturing efficiency is low since the plural concave portions (grooves) and convex portions of the Bragg grating 55 are processed one by one by a laser such as an excimer laser, etc.
Further, when the pressure of the fluid is detected at plural measuring points, sets of the light emitting element and the optical type pressure sensor 50 must be used by the number of measuring points. Therefore, a problem also exists in that cost is taken.